Golf club head

ABSTRACT

A hollow club head having a head body  14  and a face member  16  bonded to the face opening  12  of the head body  14  is provided, wherein the W/H ratio between the maximum height H (mm) and maximum width W (mm) of the face member is in the range of 1.0 to 1.7, so as to improve cost efficiency associated with improved repulsive speeds of balls hit by the club.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a hollow golf club head comprising a head body and a face member bonded to a face opening of the head body.

2. Description of Related Art

Conventional hollow golf club heads comprise a head body and a face member bonded to the face opening of the head body. Examples of face members for such hollow golf club heads include those entirely covering the face portion and those having a shape that approximates the shape of the face surface and that fits within the face surface (for example, see JP 2001-259091 A).

SUMMARY OF THE INVENTION

However, since the conventional face member is supported by the head body at the periphery of the face portion, a large improvement of repulsive performance cannot be expected by increasing the maximum width W of the face member unless the maximum height H, which is usually smaller than the maximum width, is also increased.

Titanium and titanium alloys, which are lightweight and have high strength, are often used for club heads in order to increase the volumes of club heads. While it is particularly effective to use a material having a low elastic modulus for the face member in order to improve the repulsive performance, such materials are generally expensive. Consequently, the face member becomes expensive among all parts in golf clubs since a material with particularly low elastic modulus and high strength is used for it.

It is therefore desirable to reduce the manufacturing cost by efficiently improving the repulsive performance of the face member.

The object of the invention is to provide a hollow club head having a face member bonded to the head body so as to cover the face opening of the head body, according to which the repulsive performance associated with the face member is efficiently improved without undue increases in material and/or manufacturing costs.

The invention provides a hollow club head comprising a head body having a face opening and a face member for closing the face opening, wherein the W/H ratio of the face member between the maximum height H (mm) and maximum width W (mm) is in the range of 1.0 to 1.7.

According to the present invention, the repulsive performance of the face member may be insufficient when the W/H ratio is in the range of 1.0 to 1.7. The range of the W/H ratio is preferably 1.0 to 1.5, more preferably 1.0 to 1.4.

According to the present invention, the maximum height H of the face member is preferably in the range of 47 to 65 mm, and more preferably 50 to 60 mm. The repulsive performance of the face member may be insufficient when the maximum height H of the face member is outside the range of 47 to 65 mm. The maximum width of the face member is preferably in the range of 47 to 110 mm and more preferably in the range of 47 to 91 mm.

According to the present invention, the maximum height L of the face portion is preferably in the range of 53 to 65 mm, more preferably 55 to 60 mm. The repulsive performance of the face member may be insufficient when the maximum height L of the face portion is outside the range of 53 to 65 mm.

One or both of the top and bottom edges of the face member may be extended at some portions beyond the face portion. For example, the top edge of the face member may extend into the crown portion beyond the face portion. Also, the bottom edge of the face member may extend into the sole portion of the club head. Since the position of the centroid of the face member goes up by extending the top edge of the face member into the crown portion, if the top edge of the face member enters into the crown portion, a point on the face portion onto which the center of gravity of the head is projected along a line that is normal to the face portion (or the front surface of the face member) may become close to the centroid of the face member, or such a projected point of the center of gravity of the head may coincide with the centroid position of the face member. Consequently, the face member can sufficiently yield when the golf club strikes a golf ball at the face member so as to increase the carry of the ball and improve the feeling of the shot.

A point onto which the actual center of gravity of the club head is vertically projected on the face portion is sometimes referred to as the projected position of the center of gravity on the face portion, while the position of the centroid refers to a point corresponding to an action point which sums up all presumed forces coming from every part or area of a figure or shape. Preferably, the distance between the centroid of the face member and the center of gravity of the club head falls within the range of 0 to 5 mm, more preferably within the range of 0 to 3.5 mm. This is because impact forces are better transmitted to the ball if the center of gravity and the centroid of the face member are relatively close to each other as the repulsiveness of the face member is generally high around its centroid.

The club head according to the present invention may have differing thicknesses at different points on the face member. Since the hitting surface of the face member has to be flat or uniformly bent, such differences in the thickness of the face member may cause the back of the face member to have inclined portions. By having the thickness of the face member change at some portions of the face member, the repulsion characteristics of the face portion may be improved. In this case, it is preferred to design the contour of the back of the face member so as to provide a region of the maximum thickness and a region of the minimum thickness on the face member with an incline area or surface connecting the two regions.

The thickness at this inclined area or surface may change continuously or discontinuously within itself and also connecting with either of the two regions of the maximum and minimum thickness. Also, the thickness of the region of the maximum thickness and that of the region of the minimum thickness may be uniform within each region.

The region of the maximum thickness may be located surrounded by the region of the minimum thickness so that the region of the maximum thickness forms an island with the inclined area or surface connecting the two regions. Preferably, the centroid of the face member and/or face portion falls within the region of the maximum thickness for better repulsive characteristics, etc.

The maximum thickness of the face member may preferably be 2.1 to 4.5 mm and more preferably 2.5 to 3.6 mm. Also the minimum thickness of the face member may preferably be 1 to 2.6 mm and more preferably 1.3 to 2.1 mm if the face member has regions of differing thicknesses. The rigidity of the face portion may be too high when the maximum thickness exceeds 4.5 mm, while the strength of the face portion and the ease of manufacturing the club head may deteriorate when the minimum thickness is less than 1 mm. The difference of the thickness between the two regions of the face member is preferably 0.8 to 3.5 mm and more preferably 1 to 2.5 mm.

The region of the maximum thickness may preferably occupy 2 to 12% and more preferably 2 to 8% of the area of the face portion, while the region of the minimum thickness may preferably occupy 15 to 60% and more preferably 30 to 50% of the area of the face portion in the club head. The area of the region of the maximum thickness may be 3 to 50%, preferably 5 to 30%, of that of the region of the minimum thickness. The area of the face portion is, for example, about 35 to 55 cm² if the club is #1 wood.

The head body may be integrally formed, or may be formed by a plurality of members bonded together. While the material of the head body and the method of manufacturing are not particularly restricted according to the present invention, titanium, titanium alloys, aluminum and stainless steel are preferable as materials used for club heads, while the head body may preferably be formed by casting.

While the material and the method of manufacturing the face member are also not particularly restricted according to the present invention, titanium, titanium alloys, aluminum and stainless steel may preferably used, while the face member is favorably forged or press-formed with a press.

While the method of bonding the face member to the head body is not particularly restricted according to the present invention, plasma welding, laser welding or electron beam welding is suitable for cleanly finishing bonding portions and for enhancing accuracy of the weight of the club head. Conventional plasma welding may be used for this purpose. A plasma arc generates high temperature energy sufficient to melt materials to be welded together, and the welded materials become solidified after the welding. Conventional laser welding using gas lasers such as CO laser and CO₂ laser, and solid state lasers such as YAG laser may also be used. Conventional electron beam welding with appropriate output energy may also be used according to the present invention.

When the head body is bonded to the face member by plasma, laser or electron beam welding, the gap between the head body and face member may be filled with extra metallic material that is additional to the head body and face member. If such extra material is used, the metallic members do not have to be precisely machined so that no gaps are formed between the head body and face member. Consequently, the cost required for high precision machining of the head body and face member can be saved. While the gap between the head body and face member is filled with the extra metallic material which is additional to the head body and face member, the control of the weight of the club head is relatively easy using plasma, laser or electron beam welding since no surface sink or burn-off is caused at the welded portion.

No particular restrictions are applicable to ways in which plasma, laser or electron beam welding is used to fill a gap between the head body and face member with the extra metallic material additional to the head member and face member, according to the present invention. For example, however, a wire of metallic material separate from the face member and head body may be used for filling the gap between the head body and face member, and the face member may be welded to the head body using plasma, laser or electron beams. This wire may preferably have a diameter of 0.5 to 3.5 mm and, particularly 1.0 to 2.5 mm. Also, when plasma welding is used, it is preferable to add the extra metallic material to the welded portion between the face member and head body to provide excess metal at the juncture in terms of improved welding and resulting weld strength while dimensional accuracy of the weld may slightly suffer.

The extra metallic material for filling the gap between the head body and face member may be selected from titanium, titanium alloys, aluminum and stainless steel. Although the gap material may be either similar to or the same as the metal used for one of or both the head body and/or face member, or it may also be quite different from any of the materials used for the head body and face member. Specifically, the gap material may have a composition that is different from, but 60% or more, particularly 80% or more similar to, the composition of the metal used for one or both of the head body and face member. The gap material may be the same kind of metal as those used in the head body and face member, or an alloy thereof, and may show a melting point that is different from the melting point of the material used for the head body or face member preferably by 0 to 200° C., more preferably by 0 to 150° C.

The materials for the head body and face member, and the gap material may be selected, for example, from the metals having the compositions described in (1) to (8) below, while the present invention is not restricted to such a list. The combinations of (1) and (4); (2) and (4); and (3), (4), (8) and (8) are particularly preferable.

(1) Ti735 (Ti17)

-   -   Ti-5Al-2Sn-2Zr-4Mo-4Cr (the total of metals other than Ti is         17%)

(2) SAT2041

-   -   Ti-20V-4Al-1 Sn (the total of metals other than Ti is 25%)

(3) SP700

-   -   Ti-4.5Al-3V-2Fe-2Mo (the total of metals other than Ti is 11.5%)

(4) 6-4 Ti

-   -   Ti-6Al-4V (the total of metals other than Ti is 10%)

(5) 10-2-3 Ti

-   -   Ti-10V-2Fe-3Al (the total of metals other than Ti is 15%)

(6) 15-5-3 Ti

-   -   Ti-15Mo-5Zr-3Al (the total of metals other than Ti is 23%)

(7) 15-3-3-3

-   -   Ti-15V-3Cr-3Sn-3Al (the total of metals other than Ti is 24%)

(8) SUS 630

-   -   17Cr-4Ni-4Cu—Nb (about 25% of the balance is Fe, and a minor         amount of Nb is added)

The club head of the invention preferably has a volume of 340 to 460 cm³.

The club head of the invention can be formed into a wood or an iron having a cavity. The club head of the invention can be formed into a composite club head comprising a metal and a material other than the metal, such as a fiber-reinforced resin.

The manufacturing cost of the club head can be reduced by efficiently improving repulsive performance of the face member.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view showing an embodiment of the club head according to the invention.

FIG. 2 shows an end view of the club head along the line X-X in FIG. 1.

FIG. 3 shows a perspective view of the face member of the club head shown in FIG. 1.

FIG. 4 is a magnified drawing showing the welded part of the club head in FIG. 1.

FIG. 5 is a perspective view showing an embodiment of the club head according to the invention.

FIG. 6 illustrates the face member used in the example.

FIG. 7 is a graph showing the repulsive speed of the face member used in the example.

FIG. 8 is a graph showing the repulsive speed of the face member used in the example.

FIG. 9 shows a different embodiment of the club head according to the invention, where FIG. 9(a) shows a front view and FIG. 9(b) shows a cross section of the face member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While some examples of the present invention are described below with reference to drawings, the present invention is defined in the claims and by no means restricted to such examples.

Example 1

FIG. 1 is a perspective view showing an example of the club head according to the present invention. FIG. 2 is a cross-sectional view of the club head along the arrow line X-X in FIG. 1, and FIG. 3 is a perspective view of the face member of the club head. The club head of this embodiment is formed into a wood having an internal cavity.

The club head of this example comprises a head body 14 made of a titanium alloy (specifically, 6-4 Ti cast material), and a face member 16 made of a titanium alloy (specifically, Ti 735 rolled material) for closing a face opening 12 of the head body 14.

The top edge 12 of the face opening and the top edge of the face member 16 reach the crown portion of the club head. Accordingly, the top edge 18 of the face member 16 serves as a part of the crown portion of the club head when the face member 16 is bonded to the periphery of the face opening 12 of the head body 14.

According to this example, the face member 16 has a maximum height H of 58.5 mm, and the face member 16 has a maximum width W of 75 mm. The W/H ratio is 1.282. The maximum height L of the face is 58.5 mm, and the head volume is 410 cm³.

The head body 14 and face member 16 are welded together using plasma while the gap between them is filled with a metallic material (specifically, a wire with a diameter of 1.5 mm made of 6-4 Ti, which is the same as the material of the head body 14). Accordingly, the gap between the head body 14 and face member 16 is filled with the extra metallic material 20.

Example 2

FIG. 5 is a perspective view showing another example of the club head according to the invention. The club head of this example is formed into a wood club head having a cavity.

The club head of this example comprises the head body 34 made of titanium alloy (specifically, a cast material of 6-4 Ti) having the face opening 32 on the face portion 30, and the face member 36 made of titanium alloy (specifically, a rolled material of SP700) for closing the face opening 32.

The top edge of the face opening 32 and the top edge of the face member 36 reach the crown portion of the club head as in example 1. Accordingly, the upper edge 18 of the face member 36 serves as a part of the crown portion when the face member 36 is bonded to the periphery of the face opening 32.

The maximum height H of the face member 36 is 54 mm, and the maximum width W of the face member 36 is 75 mm. The W/H ratio is 1.389. The maximum height L of the face portion is 59 mm, and the head volume is 415 cm³.

The head body 34 and face member 36 are welded together using laser welding while the gap between them is filled with a metallic material (specifically, a wire material with a diameter of 1.5 mm made of 6-4 Ti, which is the same as the material of the head body 34).

Experimental Results:

The advantageous effect of the invention was confirmed by the following experiments. In simulation, hollow club heads were formed by bonding the three kinds of face members shown in FIG. 6 to the face opening of the head body. The face member shown in FIG. 6(a) has a maximum height H of 50 mm and maximum width W of 50 mm with a W/H ratio of 1, the face member shown in FIG. 6(b) has a maximum height H of 50 mm and maximum width W of 85 mm with a W/H ratio of 1.7, and the face member shown in FIG. 6(c) has a maximum height H of 50 mm and maximum width W of 100 mm with a W/H ratio of 2. The material of the face member was β titanium (15-3-3-3), and the thickness of the face member was 2.8 mm. Each face member was bonded to the head body at a peripheral region of a 2 mm width (the region indicated by hatching in FIG. 6(a)) of the face member.

Repulsive speeds (initial speeds after impact) of a given ball for each club head were simulated at a collision speed of 40 m/s or 45 m/s. The specific W/H ratios for which the shapes of the face member are shown in FIG. 6 as well as other W/H ratios were used. The club was brought to the ball to collide with the ball at a centroid position of the face member. The simulation results are shown in FIG. 7 (the collision speed of the head was 40 m/s) and FIG. 8 (the collision speed of the head was 45 m/s). In FIGS. 7 and 8, the repulsive speeds are plotted for the different values, 50, 60, 70, 80 85, 90 and 100 mm of W when the maximum height is 50 mm.

The results of FIGS. 7 and 8 indicate the following facts. Repulsive force is improved by increasing the W/H ratio from 1.0 to 2.0. However, repulsive forces are not in a linear relation to the W/H ratio, and the plot of the relation between the repulsive force and W/H ratio falls on a curved line having an inflection point on the curve. As shown in FIGS. 7 and 8, the increasing rate of repulsive force in the range of the W/H ratio of 1.0 to 1.7 is different from the increasing rate of repulsive force in the range of the W/H ratio of 1.7 to 2.0, and the graphs show that there are points near the W/H ratio of 1.7 where the slope becomes more moderate. Accordingly, the appropriate W/H ratio for efficiently increasing the repulsive force is in the range of 1.0 to 1.7 against increasing costs associated with materials used for larger face members. For example, if the height H of the face member is fixed, as the width W of the face member increases, the cost of a material used to form the face member also increases. If improvements in repulsive performance are higher for the same increase in the material cost, the overall cost effectiveness is improved.

Example 3

An example is given for the club head that has differing thicknesses of the face member. On the back side of such a face member an inclined portion is provided as shown in FIG. 9. FIG. 9 shows a club head having a face member that has an inclined portion on the back surface. FIG. 9(a) shows a front view and FIG. 9(b) shows a corresponding cross-sectional view of the face member. The club head comprises a head body 124 having a face opening 122 in the face portion 120, and a face member 126 for closing the face opening 122. A region 128 having the maximum thickness and another region 130 having the maximum thickness are formed on the back surface of the face member 126, and the inclined portion 132 where the thickness continuously changes is provided between the two regions 128 and 130. The region 128 having the maximum thickness contains the centroid of the face portion 120. These regions 128 and 130 may have a circular shape or an ellipsoidal shape which is elongated in the width directed on the face member. The inclined portion 132 is located at the outside of the region 128 having the maximum thickness, and the region 130 having the minimum thickness is located at the outside of the inclined portion 132.

Specifically, the maximum thickness Tmax is 3.1 mm, and the minimum thickness Tmin is 1.8 mm. The region having the maximum thickness occupies 2.3% of the area of the face portion, while the region having the minimum thickness 48%. In anther example, the maximum thickness Tmax is 3.4 mm and the minimum thickness Tmin is 2.3 mm while W_(IF) is 15 mm and W_(I) is 70 mm with the maximum height of the face member 57.2 mm, the maximum width W of 76.7 mm and the maximum height H of 53.7 (W/H=1.43). Both the face member and head body are made of a titanium alloy. 

1. A club head comprising a hollow head body having a face opening at the face portion and a face member that closes the face opening, wherein a W/H ratio of a maximum width W to a maximum height H of the face member is in a range of 1.0 to 1.7.
 2. The club head according to claim 1, wherein the maximum height H of the face member is in the range of 47 to 65 mm.
 3. The club head according to claim 1, wherein the maximum width of the face member is in the range of 47 to 110 mm.
 4. The club head according to claim 1, wherein the maximum height L of the face portion is in a range of 53 to 65 mm.
 5. The club head according to claim 1, wherein one or both of the top and bottom edges of the face member are extended beyond the face portion.
 6. The club head according to claim 1, wherein a distance between a centroid of the face member and a point on the face portion onto which a center of gravity of the head is projected along a line that is normal to the face portion is in the range of 0 to 5 mm.
 7. The club head according to claim 1, wherein the head body is formed by casting and the face member is formed by forging or press-forming.
 8. The club head according to claim 1, wherein the head body and face member are welded together using plasma, laser or an electron beam.
 9. The club head according to claim 7, wherein a gap between the head body and face member is filled with a metallic material that is different from materials of the head body and face member.
 10. The club head according to claim 1, wherein a volume of the club head is in the range of 340 to 460 cm³.
 11. The club head according to claim 1, wherein the club is made of a metallic material and a non-metallic material.
 12. The club head according to claim 1, wherein a back of the face member has an inclined portion where a thickness of the face member varies.
 13. The club head according to claim 12, wherein a region having a maximum thickness and a region having a minimum thickness are formed on the back of the face member, with an inclined portion being provided between the two regions.
 14. The club head according to claim 13, wherein the thickness of the inclined portion changes either continuously or discontinuously with respect to any of the two regions or within the inclined portion.
 15. The club head according to claim 12, wherein the inclined portion is formed outside the region having the maximum thickness, while the region having the minimum thickness is formed outside the inclined part. 